Non-flammable, conductive, and stretchable organic-ionogel for solid-state polymer lithium metal batteries

Abstract

Gel polymer electrolytes (GPEs) have been brought into the spotlight as next-generation electrolytes for batteries in the realm of flexible and wearable electronic devices. However, challenges remain in achieving a trade-off between high safety, high ionic conductivity, and superior mechanical stretchability concurrently. To conquer it, the ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide; EMIM-TFSI), coupled with the organic fluorinated solvent (N,N-dimethyl trifluoroacetamide; FDMAC), is proposed for designing a neotype organic-ionogel (OIG) with a rigid-flexible vinylene carbonate (VEC)-butyl acrylate (BA) cross-linked copolymer as the polymer skeleton. By structural optimization and component regulation, the optimal OIG-15 % presents the enhanced ionic conductivity (5.5 × 10⁻⁴ S cm⁻¹), non-flammability, and prominent mechanical stretchability, especially sustaining an elongation at break of 427 % and volumetric compressibility exceeding 85 %. Consequently, the Li||Li symmetric cell assembled with OIG-15 % can demonstrate stable cycling for over 2000 h at a current density of 0.1 mA cm⁻², while the Li|OIG-15 %|LiFePO₄ cell can still maintain an exceptional capacity retention of nearly 100 % after 450 cycles at 0.5C. This work provides a valuable construction strategy for the development of high-quality gel electrolyte materials, paving the way for breakthroughs in the widespread application for solid-state polymer lithium metal batteries.